Strong and anti-freezing alginate-based hydrogel with humidity response and wide-temperature-range strain sensing ability

To get strong and anti-freezing hydrogel with multiple contact and non-contact sensing performance, a facial method is proposed in this work using multiple physical bonding crosslinking and glycerol (GL) immersing strategy. The obtained hydrogels show a tensile stress at break of 5.4 MPa, an elongation at break of 1420 %, and a compression strength of 12.2 MPa at 80 % strain. Additionally, benefiting from the GL immersing the hydrogel shows superior anti-freezing (no ice formation at -60 degree celsius) and water retention ability (water loss less than 17 % after storing at 50 degree celsius for 7 h). Furthermore, the volume resistance of hydrogels exhibits excellent responses against humidity, temperature, strain, and stress. The variation of the resistance against temperature can be well described by the Arrhenius equation with an activation energy of 501.3 meV, verifying a band-gap dominated diffusion hopping conductive mechanism of the hydrogel. The sufficient humidity and temperature responses make the hydrogel applicable as a non-contact sensor, and the wide temperature strain sensing (-40 to 50 degree celsius) and stress sensing capability ensures that the hydrogel can be used as a contact sensor, ensuring that the hydrogel can be used as perfect flexible sensor for monitoring human motion and physiological signals.